Oryzomys xanthaeolus ica Osgood, 1944

Prado, Joyce Rodrigues Do & Percequillo, Alexandre Reis, 2016, Systematic studies of the genus Aegialomys Weksler, Percequillo and Voss, 2006 (Rodentia: Cricetidae: Sigmodontinae): Annotated catalogue of the types of the species-group taxa, Zootaxa 4144 (4), pp. 477-498 : 492-494

Oryzomys xanthaeolus ica Osgood, 1944

Holotype. FMNH 53157, a female specimen, deposited at The Field Museum, collected by C. C. Sanborn, in 17.I.1942 ( Fig. 7 ).

Type condition. Specimen preserved in skin and skull; both of them are in excellent condition, without any broken part.

Type material. The type material consists of two specimens: the holotype, described above, and the paratype ( FMHN 53158), an adult female.

Type locality. Hacienda San Jacinto , near Ica, Province of Ica, southwestern Peru . The geographical coordinates of this locality are 14°09’S, 75°45’W. The type locality is represented in figure 3.

Original description. Osgood described Oryzomys xanthaeolus ica in the Zoological Series of the Field Museum of Natural History, vol. 29, n.13, 1944:192–193, providing the following simplified characterization:

“Similar in color and general characters to O. x. xanthaeolus but somewhat larger and having a skull with definitely larger audital bullae.”

Original dimensions. Total length: 325 mm; tail: 161 mm; hindfoot: 33 mm. Skull-greatest length: 44.8 mm; zygomatic breadth: 19.3 mm; breadth of braincase: 13.5 mm; interorbital space: 6.1 mm; nasals: 14.3 x 4.5 mm; diastema, 8.5 mm; palatine foramina: 7.3 mm; upper toothrow, 5.5 mm. Other craniodental measurements are in table 2.

Morphological description. Dorsal pelage soft, lax, dense and long; yellowish to ochraceous wool and cover hairs, intensely grizzled with brown guard hairs, resulting in dorsal color ochraceous cream grizzled with brown; venter grayish cream; tail slightly shorter than head and body length, densely covered with hairs, weakly bicolor, with large scales with approximately 18 scales/cm and without terminal tuft; pes covered by very long and white hairs; ungual tufts dense and long, white; interdigital and plantar pads developed, thenar and hypothenar fleshy; pinnae with few external hairs and with a creamy and yellowish coloration and inner hairs light yellow.

Skull very large and robust, with moderately long and broad rostrum (approximately 36% of skull length [LN/ ONL ratio]); zygomatic plate moderately projected anteriorly, not reaching beyond nasolacrimal capsule; rostral fossa very deep; moderately projected plate and very deep fossa, configuring a moderately deep and very wide zygomatic notch; interorbital region strongly diverging posteriorly, with strongly beaded supraorbital margins; zygomatic arches strongly divergent posteriorly, wider near the squamosal root; braincase elongated, with temporal margins squared, without crests; interparietal short and wide; fronto-squamosal suture contiguous with frontoparietal suture; alisphenoid strut absent; anastomotic channel present, configuring pattern 3 of carotid circulation ( Voss 1988); parietals expanding over surface side of skull; postglenoid foramen apparently small; incisive foramen long, wider medially, with anterior and posterior margins slightly acute, posterior margin reaching anterocone of M1; posterior margin of zygomatic plate situated anterior to the alveolus of M1; palate intermediate, with deep posterolateral palatal pits recessed in deep and large palatine depressions; palate apparently without palatal excrescencies; mesopterygoid fossa perforated by very large sphenopalatine vacuities on the presphenoid and basisphenoid; auditory bulla large, with very short and narrow stapedial process.

Upper incisors opisthodont; upper molars with labial and lingual cusps arranged in opposite pairs; M1 with anteroloph short and narrow, almost entirely fused to anterocone; anterocone apparently with shallow anteromedian flexus; paracone connected medially to protocone; median mure more labially positioned, defining a long and deep hypoflexus; paracone connected labially to mesoloph, forming a small, round and labially positioned mesofosset; mesoloph moderately long, connected with median mure medially; mesoloph separated from metacone by metaflexus; M2 similar to M1, but with median mure more medially positioned; paracone connected medially to protocone; mesoloph long, connected labially to paracone, forming a small, rounded and slightly oblique mesofosset; M3 small, triangular.

Observations. According to Osgood (1944) specimens of O. xanthaeolus ica are in overall larger and have a large auditory bulla when compared with the O. xanthaeolus from nearby localities. After its original description, O. xanthaeolus ica remained as a subspecies of O. xanthaeolus until the early 1990’s, when Musser and Carleton (1993) synonymized it with O. xanthaeolus in the catalogue “Mammal Species of the World” (Wilson & Reeder 1993).

Figures

FIGURE 7. Dorsal, ventral and lateral views of the skull, and lateral view of the mandible of the specimen FMNH 53157, holotype of Oryzomys xanthaeolus ica Osgood, 1944 (ONL: 32.88 mm).